The Wolf was getting too big. So the Gods decided to put it in chains. But the wolf was aware that something was off and demanded that a God would put his arm in his mouth. Tyr was the only one who was brave enough to do so. They succesfully chained up the Fenrir but Tyr lost his arm.

Not that I mean to argue with you, but wasn't Jormungand known as the World Serpent because he grew large enough to encircle the world and grab his own tail (which kept the world together), and when he let go, the world would end (Ragnarok). Incidentally, he lets go when he is slain by Thor, at which point he poisons the sky and kills Thor in the process, setting in motion the beginning of the end?

Well, Jormungaard was killed by Thor, But in doing so, Jormungaard poisoned Thor, killed him, then ended the world, Because Jormungaard was the serpent that wrapped himself around the world and when we stopped biting his tale, Ragnarok would unfold, Also didn't Fenrir kill Odin? I kinda read up on this...

I am trying to refrain from Ragnarok since ragnarok hasn't been hit yet during the movie "Avengers" Which means that Thor is alive and ODin is also alive since he was in the movie Thor.
It is foretold that Fenrir will kill Odin during ragnarok. But Fenrir have already taken Tyr's arm. Tyr stuck his arm into the wolves mouth in order to proove that the animal was harmless. Jokes on him.